In the demo version, you can overhear two Stormtroopers talk, about the difference between regular Blaster rifles and Carbine ones, and at the end of it, one of them mentions being transferred to the Cairn installation. In the full version of the game, this same conversation is heard... during the player's time in the Cairn installation.
The Aurbesh symbols used in the Communications Code aboard the Doomgiver actually read THX.
THX 1138 reference: when the transport from Bespin arrives at the Cairn installation, the ship's call sign is 1138.
First game of the series to use the id Tech 3 (AKA "Quake III Arena") game engine. The same engine was used for the sequel, "Jedi Academy", as well as both "Star Trek: Elite Force" games. In contrast, "Dark Forces" and "Dark Forces 2: Jedi Knight" used the Jedi and Sith game engines respectively.
Though not the last of the "Dark Forces" games, it was the last to feature a level set on the notorious "Smuggler's Moon" of Nar Shadaa. Though all of the previous games had levels set there, Nar Shadaa was omitted from the next game, "Jedi Academy" likely because that game features a level on the similar setting of Coruscant. Given the choice between the 2, Coruscant was the likely choice because of its importance in the prequel trilogy, which was still unfolding when Jedi Academy was released.